The degeneration of the intervertebral disk, in particular, the degeneration of the nucleus pulposus, results in a loss of height in the affected disk space which is associated with a weakening of the annulus fibrosus and of the ligaments. As a consequence the spinal column becomes instable and is more susceptible to horizontal displacement of the vertebral bodies with respect to one another. This horizontal movement of vertebral bodies results in impairments of the nerve roots in this region and/or of the spinal marrow with pain resulting therefrom.
The principle treatment of these symptoms consists of the surgical removal of the nucleus pulposus and the insertion of support bodies in order to restore the normal height of the disk space. While there are a number of traditional systems and methods for inserting support bodies, there are a variety of demands on both the surgeon performing an intervertebral disk procedure and on the spinal spacers themselves.
A Transforaminal Lumbar Interbody Fusion (TLIF) is a surgical procedure that uses a posterior and lateral approach to access the disc space and insert a spacer. To gain access to the disc space, typically a facet joint is removed and access is gained via the nerve foramen. While more technically demanding of the surgeon than other fusion techniques, a TLIF offers a number of clinical advantages.
When compared to a PosteroLateral Fusion (PLF), a TLIF approach leaves much more of the soft tissue intact, which is less traumatic for the patient. Further, a PLF does not provide access to the disc space.
While a PosteroLateral InterBody Fusion (PLIF) provides access to the disc space, a TLIF approach also provides access to the interbody space, but without the need for manipulation of neural elements, reducing the risk of post-operative neural deficit. Additionally, in a TLIF, only a single spacer is placed. More specifically the TLIF spacer is placed in the anterior aspect of the disc space, thus providing space for a substantial fusion mass in the posterior aspect of the disc space where the natural compression occurs.
However, traditional TLIF procedures do suffer from a number of shortcomings. For example, traditional interbody spacers are coupled to an inserter by stationary threads formed in the body of the interbody spacer. Furthermore, in order to place the desired spacer in the anterior aspect of the disc space from an oblique posterior approach, traditional procedures demand that the spacer be released from the inserter and then tamped into place. The two step insertion of this spacer is generally recognized among surgeons as cumbersome and may cause unneeded damage to bone and tissue, thereby increasing patient discomfort and increasing the amount of time sufficient to complete healing.